The present invention is directed to a flywheel and crank apparatus having a pair of flywheels separated by a non-axially aligned crank for use in motorcycle engines and the like.
Many types of engines, pumps and related devices utilize a pair of flywheels which are mounted so as to rotate a common axis thereof. Also aligned along the axis of rotation of the flywheels is at least one shaft which provides power either from or to the flywheels. The flywheels are spaced by a crank throw, pin or shaft which is offset from the axis of rotation of the flywheels. A piston rod or similar device is attached to and rotates about the crank shaft, normally to convert between linear motion at a piston to a rotary motion at the flywheels. The power taken in and given off may in theory move in either direction across the machine.
For some types of split flywheel motors operating at low RPM's and under comparatively light loads, the power associated with the motor is not extremely great and does not present significant problems at the crank shaft. However, some devices of this type are designed to utilize a substantial amount of power which applies substantial forces at the juncture of the flywheels with the crank shaft. A good example of a motor of this type is a racing motorcycle having an engine of this type placed under substantial strain. Quite substantial power loadings can and are placed upon the motorcycle engine during operation and forces oil to twist the flywheels relative to the connecting crank shaft. Because the crank shaft is offset with respect to the axis of rotation of the flywheels and because of other factors found in engines of this type, it is very difficult to maintain proper coaxial alignment of the flywheels.
In particular, the flywheels may become unevenly spaced therebetween such as when they toein opposite the crank shaft or when they toeout opposite the crank shaft. An example of toein can be seen in FIG. 6 of the drawings showing prior art. The flywheels may also rotate relative to one another about an axis associated with the crank shaft so as to no longer have a common axis of rotation. In all three instances noted, the flywheels have axes of rotation which are no longer commonly aligned which leads to at best an imbalance in the engine and a reduction of power. In a worst case scenario, the misalignment of the axes of rotation of the flywheels can lead to catastrophic destruction of the engine.
Historically, flywheels of this type have often been separated by crank shafts that have tapered opposite ends and which are designed to set in a similarly tapered bore in each of the flywheels. To initially align the flywheels so that they are co-axle relative to one another, they are placed in a trueing stand having plates that hold the flywheels generally parallel to one another while nuts holding the opposite ends of the crank shaft to the flywheels are tightened. Trueing in this manner is a laborious and difficult procedure. Even with use of the trueing stand, it is difficult to get the best alignment. Also, a very high torque must be applied to the nuts in order to try to prevent slippage, for example 600 pounds per square inch torque, which often damages threads associated therewith. Keys or splines are sometimes used to help prevent turning of the crank shaft relative to the flywheels, but this does not prevent slippage such that the crank shaft axes is no longer parallel to the axes of rotation of the flywheels. Even when the torque applied to the nuts is very high, there is normally some slippage that occurs over time during usage.
Even if a manufacturer or mechanic is able to correctly align the flywheels relative to the crank shaft upon assembly of the device, the application of a large load or just extended usage of the device normally leads to misalignment of the flywheels. Consequently, it is desirable to provide a dual flywheel and crank shaft apparatus that effectively and positively properly positions the flywheels relative to one another and which resists misalignment of the flywheels during use.